WO 99/36746 discloses a device for contactless measurement of parameters of a linear textile formation such as yarn, thread, textile fiber, silver, etc. in which a linear textile formation moves in a radiation flux between a radiation source and a radiation sensor consisting of a plurality of radiation-sensitive elements arranged next to each other in a row. The device determines the diameter and/or the hairiness and/or the density etc. of the linear textile formation on the basis of the number of overshadowed radiation-sensitive elements. The radiation sensors used are CCD sensors sensing the linear textile formation discontinuously in very short sections, each of about 10 μm of its length.
The drawback consists in that as a matter of fact only a minimum of the total length of the linear textile formation is really measured. The values determined on the very short sections of the measured linear textile formation, for instance, when measuring yarn thickness have to be integrated in a complicated way prior to the processing proper in order to eliminate or at least to minimize the influence of coincidental events arising during the measurement of the very short sections of the linear textile formation and so to achieve the required measurement precision of the parameters of the linear textile formation. This is due to the fact that the yarn moves at a given velocity such as 1 m.s−1 whereas the current sensing velocity of the linear textile formation by means of CCD sensors is about 1× in 1 ms. Since the radiation-sensitive elements of CCD sensors used for contactless measurement of a linear textile formation are about 10 μm×10 μm in size, this measurement device, when applied to a linear textile formation moving, for instance, at 1 m.s−1 effectively manage to measure as little as 1% of the total length of the linear textile formation which especially nowadays has proved to be insufficient.
DE 195 32 767 A1 and EP 0 112 475 A1 disclose radiation sensors whose radiation-sensitive elements are shaped rectangularly and whose length is superior to their width. However, in view of both the dimensions of the radiation-sensitive elements which are in EP 0 122 475 A1 in the order of millimeters and of the design of the sensors, these sensors are unfit for use in the measurement of the parameters of a linear textile formation such as yarn, thread, textile fiber, silver, etc.